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B24D3/00—Physical features of abrasive bodies, or sheets, e.g. abrasive surfaces of special nature; Abrasive bodies or sheets characterised by their constituents

B24D3/02—Physical features of abrasive bodies, or sheets, e.g. abrasive surfaces of special nature; Abrasive bodies or sheets characterised by their constituents the constituent being used as bonding agent

B24D3/20—Physical features of abrasive bodies, or sheets, e.g. abrasive surfaces of special nature; Abrasive bodies or sheets characterised by their constituents the constituent being used as bonding agent and being essentially organic

B24D3/28—Resins or natural or synthetic macromolecular compounds

B—PERFORMING OPERATIONS; TRANSPORTING

B24—GRINDING; POLISHING

B24D—TOOLS FOR GRINDING, BUFFING, OR SHARPENING

B24D3/00—Physical features of abrasive bodies, or sheets, e.g. abrasive surfaces of special nature; Abrasive bodies or sheets characterised by their constituents

C08F290/00—Macromolecular compounds obtained by polymerising monomers on to polymers modified by introduction of aliphatic unsaturated end or side groups

C08F290/02—Macromolecular compounds obtained by polymerising monomers on to polymers modified by introduction of aliphatic unsaturated end or side groups on to polymers modified by introduction of unsaturated end groups

C08L63/00—Compositions of epoxy resins; Compositions of derivatives of epoxy resins

Abstract

Coated abrasive articles comprise a backing and an abrasive layer, and optionally at least one of a backsize layer, tie layer, supersize layer, presize layer, or saturant. The coated abrasive article comprises a reaction product of components comprising:

polyfunctional acrylate;

polyfunctional cationically polymerizable material;

free radical photoinitiator;

triarylsulfonium salt having the formula

wherein R1, R2 and R3 independently represent an, optionally substituted, aromatic group having from about 4 to about 20 carbon atoms, and Y− represents a non-interfering anion; and

quaternary ammonium salt having the formula

wherein X− is a non-interfering anion.

Description

TECHNICAL FIELD

The present invention relates to coated abrasive articles and to methods of making and using the same.

BACKGROUND OF THE INVENTION

In general, coated abrasive articles have abrasive particles secured to a backing. More typically, coated abrasive articles comprise a backing having two major opposed surfaces and an abrasive layer secured to a major surface. The abrasive layer is typically comprised of abrasive particles and a binder, wherein the binder serves to secure the abrasive particles to the backing.

One common type of coated abrasive article has an abrasive layer which comprises a make layer, a size layer, and abrasive particles. In making such a coated abrasive article, a make layer comprising a first binder precursor is applied to a major surface of the backing. Abrasive particles are then at least partially embedded into the make layer (e.g., by electrostatic coating), and the first binder precursor is cured (i.e., crosslinked) to secure the particles to the make layer. A size layer comprising a second binder precursor is then applied over the make layer and abrasive particles, followed by curing of the binder precursors.

Another common type of coated abrasive article comprises an abrasive layer secured to a major surface of a backing, wherein the abrasive layer is provided by applying a slurry comprised of binder precursor and abrasive particles onto a major surface of a backing, and then curing the binder precursor.

Optionally, coated abrasive articles may further comprise, for example, a backsize layer (i.e., a coating on the major surface of the backing opposite the major surface having the abrasive layer), a presize layer or a tie layer (i.e., a coating between the abrasive layer and the major surface to which the abrasive layer is secured), and/or a saturant which coats both major surfaces of the backing. In another aspect, coated abrasive articles may further comprise a supersize layer covering the abrasive layer. The supersize layer typically includes grinding aids and/or anti-loading materials.

Typically, binder precursors include one or more catalyst(s), initiator(s) and/or curing agent(s) (i.e., collectively referred to as curative) that facilitates curing of the binder precursor by thermal and/or radiation curing methods. The degree of cure of binder precursor (and resulting abrasive properties of the coated abrasive article) typically depends, in part, on the composition of the curative. Generally, radiation curing methods provide rapid curing of binder precursors, but are inhibited by opaque materials such as abrasive particles and/or fillers that block incident radiation (e.g., by shadowing). Binder precursors in make, size, and/or slurry layers of the abrasive layer, and optionally in supersize, backsize, presize, and/or tie layers, and/or saturant are prone to such shadowing. Thermal methods for curing binder precursors are generally not inhibited by shadowing, but are typically slower than radiation curing methods.

A variety of abrasive properties may be associated with coated abrasive articles. One important abrasive property is “stiction”. Stiction refers to the force necessary to slide the coated abrasive article against a workpiece during use. Many users of coated abrasive articles consider high stiction aesthetically desirable, associating high stiction with other desirable abrasive performance parameters (e.g., high rate of cut).

There continues to be a need for binder precursors that are useful for making coated abrasive articles, that cure rapidly in the presence of shadowing, have acceptable pot life, and result in coated abrasive articles having improved abrasive properties such as stiction.

SUMMARY OF THE PRESENT INVENTION

In one aspect, the present invention provides a coated abrasive article comprising:

a backing having a major surface;

an abrasive layer secured to at least a portion of the major surface, the abrasive layer comprising a binder and abrasive particles; and

reaction product of components comprising:

polyfunctional acrylate;

polyfunctional cationically polymerizable material; and

ternary curative,

wherein, optionally, the binder comprises at least a portion of the reaction product.

In another aspect, the present invention provides a method for making a coated abrasive article comprising:

providing a backing having a major surface;

applying a make layer comprising a first binder precursor onto at least a portion of the major surface of the backing;

at least partially embedding a plurality of abrasive particles into the make layer;

curing the first binder precursor;

applying a size layer comprising a second binder precursor onto at least a portion of the make layer and plurality of abrasive particles; and

curing the second binder precursor to provide a coated abrasive article,

wherein said method includes incorporating a reaction product of components comprising:

polyfunctional acrylate;

polyfunctional cationically polymerizable material; and

ternary curative,

into said coated abrasive article, and wherein, optionally, at least one of the first or second binder comprises at least a portion of the reaction product.

In another aspect, the present invention provides a method for making a coated abrasive article comprising:

providing a backing having a major surface;

applying a slurry comprising a binder precursor and abrasive particles onto at least a portion of the major surface of the backing; and

curing the binder precursor to provide a coated abrasive article,

wherein said method includes incorporating a reaction product of components comprising:

polyfunctional acrylate;

polyfunctional cationically polymerizable material; and

ternary curative,

into said coated abrasive article, and wherein, optionally, the cured binder precursor comprises at least a portion of the reaction product.

In another aspect, the present invention provides a method of abrading a workpiece comprising:

providing a coated abrasive article according to the present invention;

frictionally contacting at least a portion of the abrasive layer with at least a portion of the surface of the workpiece; and

moving at least one of the coated abrasive article or the workpiece relative to the other to abrade at least a portion of the surface.

Coated abrasive articles according to the present invention are conveniently prepared and typically exhibit one or more improved abrasive properties (e.g., stiction).

As used herein:

“acrylate” includes both acrylate and methacrylate;

“acryloxy” includes both acryloxy and methacryloxy;

“actinic radiation” means particulate and non-particulate radiation and includes electron beam radiation as well as electromagnetic radiation having at least one wavelength in the range of from about 200 nanometers (nm) to about 700 nm;

“average acrylate functionality” refers to the average number of acryloxy groups per molecule; it is determined for a specified material by dividing the total number of acryloxy groups by the total number of molecules having acryloxy groups;

“average cationically polymerizable group functionality” refers to the average number of cationically polymerizable groups per molecule; it is determined for a specified material by dividing the total number of cationically polymerizable groups by the total number of molecules having cationically polymerizable groups;

“bireactive compounds” are those which contain at least one ethylenically-unsaturated group and at least one 1,2-epoxide group;

“crosslinked” means having polymeric sections that are interconnected through chemical bonds (i.e., interchain links) to form a three-dimensional molecular network;

“epoxy resin” refers to a material containing molecules having at least one epoxy group;

“epoxy group” refers to an oxiranyl group;

“oligomer” refers to a polymer molecule having 2 to 10 repeating units (e.g., dimer, trimer, tetramer, and so forth) having an inherent capability of forming chemical bonds with the same or other oligomers in such manner that longer polymeric chains can be formed therefrom;

“photoinitiator” refers to a substance, which, if exposed to electromagnetic radiation having at least one wavelength in the range of from about 200 nm to about 700 nm, forms an initiator for free radical polymerization;

“polyfunctional acrylate” refers to a material having an average acrylate functionality of at least 2;

“ternary curative” refers to a combination of components comprising:

free radical photoinitiator;

triarylsulfonium salt having the formula

wherein R1, R2 and R3 independently represent an, optionally substituted, aromatic group having from about 4 to about 20 carbon atoms, and Y− represents a non-interfering anion; and

quaternary ammonium salt having the formula

wherein X− is a non-interfering anion.

BRIEF DESCRIPTION OF THE DRAWING

The drawing is a cross-sectional view of a section of an exemplary coated abrasive.

DETAILED DESCRIPTION

An exemplary coated abrasive article according to the present invention is illustrated in the drawing. Referring to the drawing, coated abrasive article 1 has backing 2 and abrasive layer 3. Abrasive layer 3, in turn, includes abrasive particles 4 secured to major surface 7 of backing 2 by make layer 5 and size layer 6.

Suitable backings for coated abrasive articles according to the present invention include those known in the art for making coated abrasive articles, including conventional sealed coated abrasive backings and porous non-sealed backings. The thickness of the backing generally ranges from about 0.02 to about 5 millimeters, desirably from about 0.05 to about 2.5 millimeters, and more desirably from about 0.1 to about 0.4 millimeter, although thicknesses outside of these ranges may also be useful.

The backing may be flexible or rigid. Desirably the backing is flexible. The backing may be made of any number of various materials including those conventionally used as backings in the manufacture of coated abrasives.

The choice of backing material may depend, for example, on the intended application of the coated abrasive article. The thickness and smoothness of the backing should also be suitable to provide the desired thickness and smoothness of the coated abrasive article, wherein such characteristics of the coated abrasive article may vary depending, for example, on the intended application or use of the coated abrasive article.

The backing may, optionally, have at least one of a saturant, a presize layer and/or a backsize layer. The purpose of these materials is typically to seal the backing and/or to protect yarn or fibers in the backing. If the backing is a cloth material, at least one of these materials is typically used. The addition of the presize layer or backsize layer may additionally result in a “smoother” surface on either the front and/or the back side of the backing. Other optional layers known in the art may also be used (e.g., tie layer; see, e.g., U.S. Pat. No. 5,700,302 (Stoetzel et al.), the disclosure of which is incorporated by reference).

An antistatic material may be included in any of these cloth treatment materials. The addition of an antistatic material can reduce the tendency of the coated abrasive article to accumulate static electricity when sanding wood or wood-like materials. Additional details regarding antistatic backings and backing treatments can be found in, for example, U.S. Pat. Nos. 5,108,463 (Buchanan et al.); 5,137,542 (Buchanan et al.); 5,328,716 (Buchanan); and 5,560,753 (Buchanan et al.), the disclosures of which are incorporated herein by reference.

The backing may be a fibrous reinforced thermoplastic such as described, for example, as described, for example, in U.S. Pat. No. 5,417,726 (Stout et al.), or an endless spliceless belt, as described, for example, in U.S. Pat. No. 5,573,619 (Benedict et al.), the disclosures of which are incorporated herein by reference. Likewise, the backing may be a polymeric substrate having hooking stems projecting therefrom such as that described, for example, in U.S. Pat. No. 5,505,747 (Chesley et al.), the disclosure of which is incorporated herein by reference. Similarly, the backing may be a loop fabric such as that described, for example, in U.S. Pat. No. 5,565,011 (Follett et al.), the disclosure of which is incorporated herein by reference.

In some instances, it may be desirable to incorporate a pressure-sensitive adhesive onto the back side of the coated abrasive article such that the resulting coated abrasive article can be secured to a back up pad. Exemplary pressure-sensitive adhesives include latex crepe, rosin, acrylic polymers, and copolymers including polyacrylate esters (e.g., poly(butyl acrylate)), vinyl ethers (e.g., poly(vinyl n-butyl ether)), alkyd adhesives, rubber adhesives (e.g., natural rubber, synthetic rubber, chlorinated rubber), and mixtures thereof.

Exemplary rigid backings include metal plates, ceramic plates, and the like. Another example of a suitable rigid backing is described, for example, in U.S. Pat. No. 5,417,726 (Stout et al.), the disclosure of which is incorporated herein by reference.

To promote adhesion of the make layer, slurry layer, and/or optional backsize layer, it may be necessary to modify the surface to which these layers are applied. Exemplary surface modifications include corona discharge, ultraviolet light exposure, electron beam exposure, flame discharge, and/or scuffing.

In some embodiments of the present invention, the abrasive layer comprises make and size layers. The make or the size layers may be of any composition (e.g., phenolic, epoxy/acrylate), but desirably at least one of the make or size layer, comprises a reaction product of components comprising polyfunctional acrylate, polyfunctional cationically polymerizable material, and ternary curative.

Desirably, both the make and size layers comprise reaction product of binder precursor comprising polyfunctional acrylate, polyfunctional cationically polymerizable material, and ternary curative. The binder precursor is cured to form a binder using the methods described hereinbelow.

In some embodiments, the binder precursor comprising the make layer is desirably a hot melt adhesive as described in, for example, U.S. Pat. No. 5,436,063 (Follet et al.), the disclosure of which is incorporated herein by reference. In such embodiments, the binder precursor is typically applied to the backing as a liquid material. Abrasive particles are at least partially embedded into the liquid binder precursor which is then cured thereby fixing the abrasive particles to the make layer. A size layer, for example, a size layer comprising reaction product of binder precursor comprising polyfunctional acrylate, polyfunctional cationically polymerizable material, and ternary curative, is then applied over the make layer and abrasive particles and cured.

The basis weight of the make layer utilized may depend, for example, on the intended use(s), type(s) of abrasive particles, and nature of the coated abrasive article being prepared, but generally will be in the range of from about 1 to about 30 grams per square meter (i.e., g/m2), desirably from about 2 to about 25 g/m2, and more desirably from about 5 to about 20 g/m2. The make layer may be applied by any known coating method for applying a make layer to a backing, including roll coating, extrusion die coating, curtain coating, knife coating, gravure coating, spray coating, and the like.

The basis weight of the size layer will also necessarily vary depending on the intended use(s), type(s) of abrasive particles, and nature of the coated abrasive article being prepared, but generally will be in the range of from about 1 to about 400 g/m2, desirably from about 1 to about 300 g/m2, and more desirably from about 5 to about 300 g/m2. The size layer may be applied by any known coating method for applying a size layer to a backing, including roll coating, extrusion die coating, curtain coating, spray coating, and the like.

In some embodiments of coated abrasive articles according to the present invention, the abrasive layer comprises a slurry layer comprising abrasive particles and binder that is the reaction product of components comprising polyfunctional acrylate, polyfunctional cationically polymerizable material, and ternary curative. Slurry coating techniques are well known in the abrasive art, and include those described, for example, in U.S. Pat. Nos. 5,378,251 (Culler et al.) and 5,942,015 (Culler et al.), the disclosures of which are incorporated herein by reference.

Polyfunctional acrylate that may be utilized in practice of the present invention includes acrylate monomers, acrylate oligomers, acrylated polymers, and mixtures thereof.

The amount of polyfunctional acrylate present in binder precursors for uncured make layers, size layers, and/or slurry layers utilized in the present invention typically ranges from about 1 to about 90 percent by weight, desirably from about 4 to about 50 percent by weight, and even more desirably from about 5 to about 30 percent by weight, based on the total combined weight of polyfunctional acrylate and polyfunctional cationically polymerizable material, although amounts outside these ranges may also be useful.

Polyfunctional acrylate may comprise a blend of two or more polymerizable acrylates. If used, such blends typically comprise a plurality of various polyfunctional acrylate monomers, acrylate oligomers, and/or acrylated polymers; in some instances, such as to adjust viscosity of the binder precursor or physical properties of the cured binder, it may be desirable to include one or more monofunctional acrylate monomers in the polyfunctional acrylate. Desirably, polyfunctional acrylate, whether present as a blend of polymerizable acrylate materials or as a single component, has an average acrylate functionality of at least 2, desirably at least 2.5, more desirably at least 3.

Polyfunctional cationically polymerizable materials, useful in practice of the present invention, may be a single compound, or mixture of compounds, having one or more cationically polymerizable materials comprising individual molecules having a plurality of cationically polymerizable groups.

Desirably, cationically polymerizable materials, whether present as a blend of cationically polymerizable materials or as a single component, has an average cationically polymerizable group (e.g., epoxy, ethenoxy) functionality of at least 2, desirably at least 2.5, more desirably at least 3.

The amount of polyfunctional cationically polymerizable material present in binder precursors for make layers, size layers, and/or slurry layers utilized in the present invention typically ranges from about 10 to about 99 percent by weight, desirably from about 50 to about 96 percent by weight, more desirably from about 70 to about 95 percent by weight, based on the total combined weight of polyfunctional acrylate and polyfunctional cationically polymerizable material, although amounts outside these ranges may also be useful.

Polyepoxides that may be utilized in practice of the present invention include monomeric polyepoxides, oligomeric polyepoxides, polymeric polyepoxides, and mixtures thereof. Polyepoxide may include aromatic and/or aliphatic polyepoxides.

Aromatic polyepoxides that may be utilized in practice of the present invention include monomeric aromatic polyepoxides, oligomeric aromatic polyepoxides, polymeric aromatic polyepoxides, and mixtures thereof.

Optionally, a hydroxy-containing material may be present in binder precursors for make layers, size layers, slurry layers and/or additional layers utilized in the present invention. Exemplary hydroxy-containing materials include those described, for example, in U.S. Pat. No. 6,077,601 (DeVoe et al.), the disclosure of which is incorporated herein by reference.

Abrasive composite particles comprise abrasive grains in a binder. Exemplary abrasive composite particles are described, for example, in U.S. Pat. No. 5,549,962 (Holmes et al.), the disclosure of which is incorporated herein by reference.

The abrasive particles typically have an average diameter of from about 0.1 to about 2000 micrometers, more desirably from about 1 to about 1300 micrometers. Coating weights for the abrasive particles may depend, for example, on the binder precursor used, the process for applying the abrasive particles, and the size of the abrasive particles, but typically range from about 5 to about 1,350 g/m2.

The binder precursor may further comprise an optional bireactive polymerizable component, for example, a compound having at least one free radically polymerizable group, and at least one cationically polymerizable group. Bireactive compounds can be made, for example, by introducing at least one ethylenically-unsaturated group into a compound that already contains one or more epoxy groups, or, conversely, by introducing at least one epoxy group into a compound that already contains one or more ethylenically-unsaturated group.

If used, optional bireactive materials are desirably selected such that they do not significantly inhibit the cure of cationically polymerizable resin. Exemplary groups that may interfere with such cure include, primary, secondary and tertiary amines, amides, imides, and the like.

Ternary curative is utilized, in practice of the present invention, to facilitate cure of at least one binder precursor.

Photoinitiators that are useful for the ternary curative include those known as useful for photocuring free radically polyfunctional acrylates. Exemplary photoinitiators include α-cleavage photoinitiators such as benzoin and its derivatives such as α-methylbenzoin; α-phenylbenzoin; α-allylbenzoin; α-benzylbenzoin; benzoin ethers such as benzil dimethyl ketal (available, for example, under the trade designation “IRGACURE 651” from Ciba Specialty Chemicals), benzoin methyl ether, benzoin ethyl ether, benzoin n-butyl ether; acetophenone and its derivatives such as 2-hydroxy-2-methyl-1-phenyl-1-propanone (available, for example, under the trade designation “DAROCUR 1173” from Ciba Specialty Chemicals) and 1-hydroxycyclohexyl phenyl ketone (available, for example, under the trade designation “IRGACURE 184” from Ciba Specialty Chemicals); 2-methyl-1-[4-(methylthio)phenyl]-2-(4-morpholinyl)-1-propanone (available, for example, under the trade designation “IRGACURE 907” from Ciba Specialty Chemicals); 2-benzyl-2-(dimethlamino)-1-[4-(4-morpholinyl)phenyl]-1-butanone (available, for example, under the trade designation “IRGACURE 369” from Ciba Specialty Chemicals); titanium complexes such as bis(η5-2,4-cyclopentadien-1-yl)bis[2,6-difluoro-3-(1H-pyrrol-1-yl)phenyl]titanium (under the trade designation “CGI 784 DC”, also available from Ciba Specialty Chemicals); and mono- and bis-acylphosphines (available, for example, from Ciba Specialty Chemicals under the trade designations “IRGACURE 1700”, “IRGACURE 1800”, “IRGACURE 1850”, and “DAROCUR 4265”). 2-Hydroxy-2-methyl-1-phenyl-1-propanone is a desired photoinitiator.

Desirably, if an acylphosphine or acylphosphine oxide photoinitiator is utilized, it is combined with a photoinitiator (e.g., 2-hydroxy-2-methyl-1-phenyl-1-propanone) having a high extinction coefficient at one or more wavelengths of the actinic radiation. Such combination typically facilitates surface cure while maintaining low levels of costly photoinitiator.

Other useful photoinitiators include anthraquinones, such as anthraquinone, 2-ethylanthraquinone, 1-chloroanthraquinone, 1,4-dimethylanthraquinone, 1-methoxyanthraquinone, and the like; and benzophenone and its derivatives (e.g., phenoxybenzophenone, phenylbenzophenone).

Triarylsulfonium salts that are useful for the ternary curative include triarylsulfonium salts having the formula

wherein

R1, R2 and R3 independently represent an, optionally substituted, aromatic group (e.g., substituted or unsubstituted phenyl, thienyl, or furanyl) having from about 4 to about 20 carbon atoms. R1, R2 and/or R3 may, optionally, have one or more fused rings (for example, naphthyl, benzothienyl, dibenzothienyl, benzofuranyl, dibenzofuranyl). Exemplary substituents that may be present, in any number or combination thereof, on aromatic groups R1, R2 and R3 include, for example, alkyl having from 1 to 12 carbon atoms (e.g., for example, methyl, ethyl, dodecyl), alkoxy having from 1 to 12 carbon atoms (e.g., methoxy, ethoxy, ethoxyethoxy), halogen, aryl having from about 4 to about 16 carbon atoms (e.g., phenyl, furanyl), thioaryl having from 4 to 16 carbon atoms (e.g., thiophenyl), hydroxy, aroyl having from 4 to 16 carbon atoms (e.g., benzoyl, methoxybenzoyl).

Triarylsulfonium salts can be prepared, for example, as described in U.S. Pat. Nos. 5,709,948 (Perez et al.) and 4,256,828 (Smith), the disclosures of which are incorporated herein by reference. Useful commercially available triarylsulfonium salts include an aromatic sulfonium complex salt, available, for example, under the trade designation “FX-512” from 3M Company, St. Paul, Minn.; an aromatic sulfonium complex salt having the trade designation “UVI-6974”, available from Dow Chemical Co.; and triarylsulfonium salts having the trade designation “SARCAT” (e.g., “SARCAT CD 1010”, “SARCAT CD 1011”), available from Sartomer Co.

Triarylsulfonium salts, useful in practice of the present invention, are typically photosensitive only in the ultraviolet region (i.e., from about 200 nm to about 400 nm of the electromagnetic spectrum. However, they can be sensitized to the near ultraviolet and the visible range of the spectrum by sensitizers for known photolyzable organic halogen compounds. Exemplary sensitizers include aromatic amines and colored aromatic polycyclic hydrocarbons, as described, for example, in U.S. Pat. No. 4,250,053 (Smith), the disclosure of which is incorporated herein by reference.

Quaternary ammonium salts that are useful for the ternary curative have the formula

wherein X− is a non-interfering anion as defined above.

Quaternary ammonium salts of this type may be prepared by methods described in, for example, U.S. Pat. No. 5,070,161 (Nakano et al.), the disclosure of which is incorporated herein by reference, or may be obtained from commercial sources (e.g., under the trade designation “NACURE XC-7231” from King Industries, Inc., Norwalk, Conn.). Analyses using infrared and nuclear magnetic resonance spectroscopy of the quaternary ammonium salt marketed under the trade designation “NACURE XC-7231” indicated that an especially desirable quaternary ammonium salt is (4-methoxybenzyl)dimethylphenylammonium hexafluoroantimonate.

Ternary curative can be present in an amount in the range of from about 0.01 to about 10 weight percent, desirably from about 0.01 to about 5 weight percent, most desirably 0.1 to about 3 weight percent, based on the total amount of photocurable (i.e., crosslinkable by electromagnetic radiation) components of the binder precursor, although amounts outside of these ranges may also be useful.

Photoinitiator, triarylsulfonium salt and quaternary ammonium salt of the ternary curative (as described above) may be present in any ratio. Typically, photoinitiator is present in the ternary curative in an amount of from about 5 to about 80 weight percent, desirably from about 20 to about 60 weight percent, more desirably from about 30 to about 50 weight percent based on the total weight of ternary curative present. Typically, triarylsulfonium salt is present in the ternary curative in an amount of from about 5 to about 80 weight percent, desirably from about 20 to about 60 weight percent, more desirably from about 30 to about 50 weight percent based on the total weight of ternary curative present. Typically, quaternary ammonium salt is present in the ternary curative in an amount of from about 5 to about 40 weight percent, desirably from about 10 to about 40 weight percent, more desirably from about 15 to about 30 weight percent based on the total weight of ternary curative present.

In addition to other components, binder precursors, if present, in the various layers (e.g., make, size, slurry, supersize, backsize, presize, and/or tie layers, and/or saturant) of coated abrasive articles according to the present invention may optionally contain catalysts (e.g., thermally activated catalysts or photocatalysts), free-radical initiators (e.g., thermal initiators or photoinitiators), curing agents to facilitate cure. Such catalysts (e.g., thermally activated catalysts or photocatalysts), free-radical initiators (e.g., thermal initiators or photoinitiators), and/or curing agents may be of any type known for use in coated abrasive articles including, for example, those described herein.

Exemplary grinding aids, which may be organic or inorganic, include waxes, halogenated organic compounds such as chlorinated waxes like tetrachloronaphthalene, pentachloronaphthalene, and polyvinyl chloride; halide salts such as sodium chloride, potassium cryolite, sodium cryolite, ammonium cryolite, potassium tetrafluoroborate, sodium tetrafluoroborate, silicon fluorides, potassium chloride, magnesium chloride; and metals and their alloys such as tin, lead, bismuth, cobalt, antimony, cadmium, iron, and titanium; and the like. Examples of other grinding aids include sulfur, organic sulfur compounds, graphite, and metallic sulfides. A combination of different grinding aids can be used such as that described, for example, in U.S. Pat. No. 5,552,225 (Ho), the disclosure of which is incorporated herein by reference.

It is also within the scope of the present invention to have additional coatings (e.g., saturant, backsize layer, presize layer, tie layer, supersize layer), which may, for example, be present as continuous or discontinuous layers as dictated by the function or purpose of the material as known to one skilled in the art, and which may optionally, comprise the reaction product of binder precursor and ternary curative. For example, it may be desirable to provide a saturation coat to smooth the inherent textured surface of the paper backing material, particularly if utilizing fine grades of abrasive (e.g., ANSI grade 400 or finer). A backsize layer, which is applied to the back side of the backing, that is, the side opposite to which the abrasive particles are applied, adds body to the backing material and protects the backing material from wear. A presize layer is similar to a saturation coat except that it is applied to a previously treated backing. A supersize layer, that is, a coating applied on at least a portion of the size layer, can be added to provide, for example, a grinding aid, and/or as an anti-loading coating.

Further, with regard to the optional supersize layer, it may serve to prevent or reduce the accumulation of swarf (the material abraded from a workpiece) between abrasive particles, which can dramatically reduce the cutting ability of the coated abrasive article. Useful supersize layers desirably include a grinding aid (e.g., potassium tetrafluoroborate), metal salts of fatty acids (e.g., zinc stearate or calcium stearate), salts of phosphate esters (e.g., potassium behenyl phosphate), phosphate esters, urea-formaldehyde resins, mineral oils, crosslinked silanes, crosslinked silicones, and/or fluorochemicals. Useful supersize materials are further described, for example, in U.S. Pat. No. 5,556,437 (Lee et al.), the disclosure of which is incorporated herein by reference.

Methods for making coated abrasive articles are well known in the art.

In one method, coated abrasive articles according to the present invention can be made by applying a make layer comprising a first binder precursor onto at least a portion of a major surface of a backing. Abrasive particles are then applied to the make layer (e.g., by drop coating and/or electrostatic coating). The abrasive particles can be applied or placed randomly or in a precise pattern onto the make layer. The make layer is then cured at least sufficiently to retain the abrasive particles for the application of a size layer. The size layer comprises a second binder precursor (which may be the same as or different from the make layer binder precursor), and is applied over the make layer and abrasive particles. The second binder precursor is then cured (and, if necessary, the make layer is further cured alone or in combination with the size layer) sufficiently to make a useful coated abrasive article.

In another method, coated abrasive articles according to the present invention can be made by applying a layer of a slurry comprising binder precursor and abrasive particles onto at least a portion of a major surface of a backing. The slurry layer is then cured sufficiently to make a useful coated abrasive article.

Methods for applying make, size, and/or slurry layers to the backing, and applying optional backsize layers, tie layers, supersize layers, presize layers, or saturants are well known in the art and include, for example, roll coating (e.g., using soft rubber rolls), curtain coating, transfer coating, gravure coating, spraying, knife, die coating. Abrasive layers may be applied to the backing in a uniform or patterned manner, and may be continuous or discontinuous.

Desirably, if utilizing binder precursors comprising solid components, such precursors may be prepared by mixing some or all of the various ingredients of a binder precursor in a suitable vessel at an elevated temperature, for example, less than about 60° C., sufficient to liquify the materials so that they may be efficiently mixed, with stirring, to form the binder precursor, but without thermally degrading them (e.g., causing premature gelling).

Binder precursors utilized in practice of the present invention may be cured by exposure to thermal energy, such as heat or infrared radiation. Exemplary sources of thermal energy include ovens, heated rolls, infrared lamps, etc.

Desirably, binder precursors utilized in practice of the present invention are curable by actinic radiation and are cured by exposure to actinic radiation. In such cases, curing of the binder precursor typically begins upon exposure of the binder precursor to an appropriate source of actinic radiation, and may continue for a period of time thereafter. The energy source is selected for the desired processing conditions and to appropriately activate any optional photoinitiator and/or optional photocatalyst. Exemplary useful sources of ultraviolet and visible radiation include mercury, xenon, carbon arc, tungsten filament lamps, and sunlight. Ultraviolet radiation, especially from a medium pressure mercury arc lamp or a microwave driven H-type, D-type, or V-type mercury lamp, such as of those commercially available from Fusion UV Systems, Gaithersburg, Md., is especially desirable.

Exposure times may range, for example, from less than about 1 second to 10 minutes or more, desirably providing a total energy exposure from about 0.1 to about 10 Joules per square centimeter (J/cm2) depending upon the amount and the type of reactants involved, the energy source, web speed, the distance from the energy source, and the thickness of the make layer to be cured. Filters and/or dichroic reflectors may be used to reduce thermal energy that accompanies the actinic radiation.

Coated abrasive articles according to the present invention can be converted, for example, into belts, tapes, rolls, discs (including perforated discs), and/or sheets. For belt applications, two free ends of the abrasive sheet may be joined together using known methods to form a spliced belt. A spliceless belt may also be formed as described, for example, in U.S. Pat. No. 5,573,619 (Benedict et al.), the disclosure of which is incorporated herein by reference.

The second major surface of the backing opposite the abrasive layer may be secured to a refastenable layer. For example, a refastenable layer may be secured (e.g., heat laminated or adhesively secured to the backing). The refastenable layer may be secured to the backing prior to the application of the make layer precursor or alternatively, for example, the refastenable layer may be secured to the backing after the application of the abrasive layer.

The refastenable layer may comprise a plurality of hooks or loops (e.g., fiber loops), typically in the form of a sheet-like substrate having a plurality of hooks or loops protruding from the back side of the substrate. The hooks or loops provide a means of engagement between the coated abrasive article and a support pad that contains a complimentary hook or loop surface.

The refastenable layer may also comprise a stem web as described, for example, in U.S. Pat. No. 5,672,186 (Chesley et al.), the disclosure of which is incorporated herein by reference.

Coated abrasive articles according to the present invention are useful for abrading a workpiece. One such method includes the step of frictionally contacting a coated abrasive article with a surface of the workpiece, and moving at least one of the coated abrasive article or the workpiece relative to the other to abrade at least a portion of the surface. Examples of workpiece materials include metal, metal alloys, exotic metal alloys, ceramics, glass, wood, wood-like materials, composites, painted surfaces, plastics, reinforced plastics, stone, and/or combinations thereof. The workpiece may be flat or have a shape or contour associated with it. Exemplary workpieces include metal components, plastic components, particleboard, camshafts, crankshafts, furniture, and turbine blades.

Coated abrasive articles according to the present invention may be used by hand and/or used in combination with a machine. At least one or both of the coated abrasive article and the workpiece is moved relative to the other when abrading.

In another aspect, abrading may be conducted under wet or dry conditions. Exemplary liquids for wet abrading include water, water containing conventional rust inhibiting compounds, lubricant, oil, soap, and cutting fluid. The liquid may also contain defoamers, degreasers, and/or the like.

The present invention will be more fully understood with reference to the following nonlimiting examples in which all parts, percentages, ratios, and so forth, are by weight unless otherwise indicated.

EXAMPLES

Unless otherwise noted, all reagents used in the examples were obtained, or are available from, general chemical suppliers such as Aldrich Chemical Co., Milwaukee, Wis., or may be synthesized by known methods.

“AMOX” refers to di-t-amyl oxalate, which can be prepared by esterification of oxalic acid with t-amyl alcohol as described in Example 11 of U.S. Pat. No. 4,904,814 (Frei et al.), the disclosure of which is incorporated herein by reference;

“CPI-1” refers to a 50 weight percent solution of triarylsulfonium hexafluoroantimonate in propylene carbonate having the trade designation “UVI-6974”, available from Dow Chemical Co.;

“CTI-1” refers to a quaternary ammonium hexafluoroantimonate, having the trade name “NACURE XC-7231”, available from King Industries, Inc.;

“EPR-1” refers to a cycloaliphatic epoxide resin (average epoxy functionality of 2), having the trade designation “CYRACURE UVR-6110”, available from Dow Chemical Co.;

“EPR-2” refers to a Bisphenol-A epichlorohydrin based epoxy resin having an epoxy equivalent weight of 525-550 grams/equivalent (g/eq), an average epoxy functionality of 2, and having the trade designation “EPON 1001F”, available from Resolution Performance Products;

“EPR-3” refers to a Bisphenol-A epoxy resin having an epoxy equivalent weight of 172-179 g/eq, an average epoxy functionality of 2.2, and having the trade designation “DER 331”, available from Dow Chemical Co.;

“FRPI-4” refers to a 1:1 mixture by weight of (2,4,6-trimethylbenzoyl)diphenylphosphine oxide and 2-hydroxy-2-methyl-1-phenyl-1-propanone obtained under the trade designation “DAROCUR 4265”, obtained from Ciba Specialty Chemicals;

“FRPI-5” refers to 2,2-dimethoxy-1,2-diphenyl-1-ethanone which is a photoinitiator having the trade designation “IRGACURE 651”, obtained from Ciba Specialty Chemicals;

“PC-1” refers to η-[xylenes (mixed isomers)]η-cyclopentadienyliron(II) hexafluoroantimonate, which can be prepared according to methods as described, for example, in U.S. Pat. No. 5,059,701 (Keipert), the disclosure of which is incorporated herein by reference;

For each measurement, a water soaked specimen was securely mounted, with the abrasive layer exposed, to a backup rubber sanding block having a sanding face of 2.8 inches (7.0 cm) by 4.9 inches (12 cm). The mounted specimen was dunked into the bucket, and the abrasive surface was placed in frictional contact with the surface of the test panel. The workpiece was manually abraded with the wetted mounted specimen in stroke cycles of 15, 15, and 20 double strokes (i.e., forward and backward). While abrading the test panel, a pressure of 4 to 6 psi (28 to 41 kiloPascals) was applied to the wetted mounted specimen. The wetted mounted specimen was dunked in the bucket of warm water between cycles. Additional dunking of the test specimen into the bucket of warm water was conducted as necessary to maintain relative movement of the specimen against the workpiece during the test.

Cut Measurement

The abraded surface of the test panel was dried. The difference between the initial (i.e., before abrading) weight and the final (i.e., after abrading) weight of the dried test panel was reported as “cut”. Reported cut values represent an average of test results for 3 specimens.

Stiction Measurement

Stiction was determined according to the following rating scale (a rating of 1 corresponds to negligible stiction and a rating of 10 corresponds to very high stiction):

1 rating:

Slid easily through all 50 double strokes, negligible resistance

felt.

2-6 rating:

No extra water dunking through all 50 strokes, some

resistance felt (2 was lower resistance and 6 was higher

resistance).

7 rating:

Increased resistance felt toward the end of each cycle (i.e., 15,

15, 20 double strokes), but the cycle could be completed.

8 rating:

One or two additional water dunkings were required during

the test to maintain relative movement of the specimen against

the workpiece during the test.

9 rating:

Three to five additional water dunkings were required during

the test to maintain relative movement of the specimen against

the workpiece during the test.

10 rating:

More than five additional water dunkings were required

during the test to maintain relative movement of the specimen

against the workpiece during the test.

Reported stiction values represent an average of test results for 3 specimens.

Surface Finish Measurement (Ra and Rz)

Ra is a common measure of roughness used in the abrasives industry. Ra is the arithmetic mean of the departures of the roughness profile from the mean line. Ra was measured with a profilometer probe, which was a diamond tipped stylus, at five locations and the arithmetic mean was calculated as the average of these five measurements. In general, the lower the Ra value was, the smoother or finer the surface finish of the workpiece. The results were recorded in micrometers. The profilometer was obtained under the trade designation “SURTRONIC 3” from Rank Taylor Hobson Co., Leicester, England.

Rz is a common measure of roughness used in the abrasives industry. Rz is defined as the Ten Point Roughness Height which is the average of the five greatest vertical peak-to-valley height differences within one cutoff length. Rz is measured with the same equipment as the Ra value. The results are recorded in micrometers. In general, the lower the Rz, the smoother the finish.

Ra and Rz were measured for dried abraded test panels. Reported Ra and Rz values represent an average of test results for 3 specimens.

Preparation of Size Resins

General Procedure for Preparing Size Resins: 29.1 grams of ACR-1 and 67.9 grams EPR-1 were mixed together at room temperature. With continued stirring, remaining ingredients as indicated in Table 1 (below) were dissolved into the mixture to resulting in a size coat.

TABLE 1

COMPONENT

SIZE RESIN NO.

(parts by weight)

1

2

3

4

5

6

7

8

9

10

11

12

EPR-1

67.9

67.9

67.9

67.9

68.25

68.6

68.25

67.9

67.9

67.9

0

67.9

ACR-1

29.1

29.1

29.1

29.1

29.25

29.4

29.25

29.1

29.1

0

29.4

29.4

VE-1

0

0

0

0

0

0

0

0

0

29.4

67.9

0

CPI-1

3.0

2.0

3.0

3.0

1.5

0

3.0

4.0

0

3.0

3.0

3.0

CTI-1

0.5

1.0

0.5

0.5

0.75

1.0

0

0

2.0

0.5

0.5

0.5

FRPI-1

1.0

1.0

0

0

1.0

1.0

1.0

1.0

1.0

0

1.0

0

FRPI-2

0

0

1.0

0

0

0

0

0

0

0

0

0

FRPI-3

0

0

0

1.0

0

0

0

0

0

0

0

0

FRPI-4

0

0

0

0

0

0

0

0

0

0

0

1.0

Examples 1-7 and Comparative Examples A-E

Examples 1-7 and Comparative Examples A-E were prepared according to the following procedure:

A make resin consisting of EPR-3 (35.8 parts by weight), AMOX (0.6 part by weight), ACR-1 (14 parts by weight), CHDM (2.8 parts by weight), EPR-2 (25.2 parts by weight), PER-1 (20 parts by weight), FRPI-5 (1 part by weight), and PC-1 (0.6 part by weight) was prepared as follows:

EPR-3, ACR-1, and CHDM were placed into a container. The mixture was then placed into a water bath having a temperature in the range of from 50 to 75° C. while mixing. FRPI-5, AMOX, and PC-1 were then added with mixing. The resulting mixture (premix) was then placed in a liquid feeder and mixed with the EPR-2 and PER-1 pellets in a twin-screw extruder. FRPI-5 and PC-1 were then added with constant stirring until the make resin was thoroughly mixed.

The make resin was die extrusion coated onto BCP coated paper at a nominal coating weight of 11 grams per square meter (g/m2). The coated paper was then passed at a line speed of 30 meters per minute under a Fusion UV Systems 600 watts per inch (236 watts per centimeter) V-bulb operating at 85 percent power (nominal UVA dosage was 0.5 Joule per square centimeter (J/cm2)). Next, SiC 400 grade abrasive particles were coated onto the make layer at a nominal coating weight of 21 g/m2, and the web was passed under three radiant infrared heaters, obtained from Glenro Co., Paterson, N.J., at a nominal web temperature setting of 140° C. for 7.3 seconds.

Size resins as indicated in Table 2 (below) were applied to the above abrasive coated paper at a coating weight of 12 g/m2 using a laboratory roll coater made by Eagle Tool Co. (Minneapolis, Minn.).

TABLE 2

COMPARATIVE

EXAMPLE NO.

EXAMPLE LETTER

1

2

3

4

5

6

7

A

B

C

D

E

Size Resin Used

1

2

3

4

5

11

12

6

7

8

9

10

TEST RESULTS

Stiction

8

7.5

5.5

6.5

8

8

7.5

5.5

3.5

6

5.5

5

Cut, grams

1.50

1.29

1.17

1.24

1.28

1.26

1.16

1.27

1.20

1.35

1.29

1.19

Ra, micrometers

23

19

19

17

20

20

16

16

24

19

20

20

Rz, micrometers

140

115

117

113

128

119

106

139

133

122

119

119

The size coated paper was then passed at a line speed of 50 meters per minute under a Fusion UV Systems 600 watts per inch (236 watts per centimeter) D-bulb (nominal UVA dosage was 0.5 J/cm2). The material was subsequently thermally cured at 140° C. for 5 minutes to provide an abrasive sheet.

The abrasive sheets were evaluated according to the Off-hand Wet Abrasion Test described above. Results are listed in TABLE 2 (above).

Various modifications and alterations of this invention will become apparent to those skilled in the art without departing from the scope and spirit of this invention, and it should be understood that this invention is not to be unduly limited to the illustrated embodiments set forth herein.

Claims (49)

What is claimed is:

1. A coated abrasive article comprising:

a backing having a major surface;

an abrasive layer secured to at least a portion of the major surface, the abrasive layer comprising a binder and abrasive particles; and

reaction product of components comprising:

polyfunctional acrylate;

polyfunctional cationically polymerizable material; and

ternary curative,

wherein, optionally, the binder comprises at least a portion of the reaction product.

2. A coated abrasive article according to claim 1, wherein the abrasive layer comprises a make layer and a size layer at least partially covering the make layer.

3. A coated abrasive article according to claim 2, wherein the make layer comprises at least a portion of the reaction product.

4. A coated abrasive article according to claim 2, wherein the size layer comprises at least a portion of the reaction product.

10. A coated abrasive article according to claim 6, wherein the coated abrasive article further comprises at least one of a backsize layer, tie layer, supersize layer, presize layer, or saturant.

11. A coated abrasive article according to claim 10, wherein at least one of the backsize layer, tie layer, supersize layer, presize layer, or saturant comprises at least a portion of the reaction product.

12. A coated abrasive article according to claim 6, wherein the backing comprises one of a polymeric substrate having hooking stems projecting therefrom, or a loop fabric.

13. A coated abrasive article according to claim 2, wherein ternary curative comprises photoinitiator comprising at least one of an alpha-cleavage photoinitiator or benzophenone derivative.

14. A coated abrasive article according to claim 2, wherein ternary curative comprises triarylsulfonium salt selected from the group consisting of (4-thiophenoxyphenyl)diphenylsulfonium salts or triphenylsulfonium salts.

16. A coated abrasive article according to claim 2, wherein the coated abrasive article further comprises at least one of a backsize layer, tie layer, supersize layer, presize layer, or saturant.

17. A coated abrasive article according to claim 16, wherein at least one of the backsize layer, tie layer, supersize layer, presize layer, or saturant comprises at least a portion of the reaction product.

18. A coated abrasive article according to claim 2, wherein the backing comprises one of a polymeric substrate having hooking stems projecting therefrom, or a loop fabric.

19. A coated abrasive ankle according to claim 1, wherein the abrasive layer comprises a slurry layer comprising a binder and abrasive particles.

20. A coated abrasive article according to claim 19, wherein the polyfunctional cationically polymerizable material comprises at least one of polyepoxide or polyfunctional vinyl ether.

25. A coated abrasive article according to claim 21, wherein the coated abrasive article further comprises at least one of a backsize layer, tie layer, supersize layer, presize layer, or saturant.

26. A coated abrasive article according to claim 25, wherein at least one of the backsize layer, tie layer, supersize layer, presize layer, or saturant comprises at least a portion of the reaction product.

27. A coated abrasive article according to claim 21, wherein the backing comprises one of a polymeric substrate having hooking stems projecting therefrom, or a loop fabric.

28. A coated abrasive article according to claim 19, wherein ternary curative comprises photoinitiator comprising at least one of an alpha-cleavage photoinitiator or benzophenone derivative.

29. A coated abrasive article according to claim 19, wherein ternary curative comprises triarylsulfonium salt selected from the group consisting of (4-thiophenoxyphenyl)diphenylsulfonium salts or triphenylsulfonium salts.

31. A coated abrasive article according to claim 19, wherein the coated abrasive article further comprises at least one of a backsize layer, tie layer, supersize layer, presize layer, or saturant.

32. A coated abrasive article according to claim 31, wherein at least one of the backsize layer, tie layer, supersize layer, presize layer, or saturant comprises at least a portion of the reaction product.

33. A coated abrasive article according to claim 19, wherein the backing comprises one of a polymeric substrate having hooking stems projecting therefrom, or a loop fabric.

34. A coated abrasive article according to claim 19, wherein ternary curative comprises photoinitiator comprising at least one of an alpha-cleavage photoinitiator or benzophenone derivative.

35. A method for making a coated abrasive article comprising:

providing a backing having a major surface;

applying a make layer comprising a first hinder precursor onto at least a portion of the major surface of the backing;

at least partially embedding a plurality of abrasive particles into the make layer;

curing the first binder precursor;

applying a size layer comprising a second binder precursor onto at least a portion of the make layer and plurality of abrasive particles; and

curing the second binder precursor to provide a coated abrasive article, wherein said method includes incorporating a reaction product of components comprising:

polyfunctional acrylate;

polyfunctional cationically polymerizable material; and

ternary curative,

into said coated abrasive article, and wherein, optionally, at least one of the first or second binder comprises cc least a portion of the reaction product.

36. A method according to claim 35, wherein the make layer comprises at least a portion of the reaction product.

37. A method according to claim 35, wherein the size layer comprises at least a portion of the reaction product.

38. A method according to claim 35, wherein the polyfunctional cationically polymerizable material comprises at least one of polyepoxide or polyfunctional vinyl ether.